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Bruno Augusto

Phone: +46 31 750 2603bruno.augusto@vti.se

www.eversafe-project.eu

PartnersSwedish National Road and Transport Research Institute (VTI)

Volvo Car Corporation (VCC)

Royal Institute of Techno-logy (KTH)

Technische Universität Chemnitz (TUC)

Fraunhofer-Gesellschaft (FhG)

Bundesanstalt für Straßenwesen (BASt)

February 2015

The Eversafe ProjectThe EVERSAFE (Everyday Safety for Electric Vehicles) project focuses on the determination of safety requirements for electrically propel-led vehicles (EV). EVERSAFE is part of the European Union seventh framework programme, within the ERA-Net Transport Electromobility+ call. The project had a duration of approximately two years and was finished by the 31st of September 2014.

• The Eversafe Project

• User Expectations • Active Safety Studies, Vehicle Stability and Driver Response

• Passive Safety Studies and Battery Safety

• New Safety Requirement and Future Research

Eversafe Newsletter 2

The successful integration of elec-trically driven vehicles into Europe’s future transport system will depend on clear and transparent functio-nal and safety requirements for the vehicles and their sub-systems. These requirements play an important role in the transport system, in two ways: • The costumer needs to be confident regarding the safety of the vehicle during operation or un-foreseen events like a fire or crash. • The automotive industry must have design standards to guaran-tee performance and reliability. The EVERSAFE project was born from the desire to tackle these demands. The objective of the project is to provide safety require-ments for electrically propelled vehic-les, thus answering the current need for standardization within this area. Under the scope of the EVER- SAFE project, safety issues were categorized in two groups: • Active Safety: Vehicle stability was addressed under fault conditions which would not arise in a conventional vehicle, i.e. failures in wheel hub motors and faulty regenerative braking systems. Driver behaviour under such conditions was also analysed.

Background and Goals• Passive Safety: The project focused on issues within the fields of crash compatibility (conventional fleet with EV fleet) and Energy Storage Systems (ESS) behaviour under and after crash loads. There was also an effort to develop concepts for safety regulations, handling and testing of electric vehicles. To complement the safety analysis, there was a user evalua-tion of safety related aspects given the importance of user acceptance in market penetration. The goal of this exercise was to identify both perceived and real safety issues that need to be addressed to facilitate customer acceptance.

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User expectations

Eversafe Newsletter 2

Of crucial importance for market penetration of EV is the acceptance among potential customers. Uncerta-inty concerning several aspects (e.g. safety of batteries in crash situations, risk of electric shock) can lead to negative safety evaluations and might affect the attitudes and purchasing decisions of potential EV buyers. Bearing this in mind, methods were developed and adjusted to assess safety concerns and expectations among potential customers. To address these concerns, two focus group sessions were conduc-ted by Chemnitz University of Tech-nology (Department of Psychology). Inexperienced and experienced electric vehicle drivers were invited to discuss critical safety concerns regarding the utilization of EV. Safety concerns distributed over 4 scenario-related categories were identified from the sessions: while driving, while charging, in case of accident and due to vehicle aging. Safety-critical aspects vary both in terms of type of interaction and human involvement. A taxonomy of concerns related with EV was elabo-rated to classify and explain potential reservations among drivers.

Active Safety Studies, Vehicle Stability and Driver ResponseA fault in the powertrain of a vehicle can influence its dynamic stability during normal driving condi-tions, thus compromising safety for occupants and surrounding traffic. Vehicles with electric powertrains can be affected by different types of problems from those which can occur for vehicles with nowadays conventional powertrains. This further motivates the need to investi-gate issues which might arise for EV and what their consequences might be. With this in mind, different types of faults in the electric power train of EV were studied and reproduced in a full vehicle simulation study. Analysis of the results thereby collected, showed that the faults have diverse influences on vehicle stability. These were grouped in fault classes based on the severity of their consequences. Three typical faults in an electric power train were later selected, i.e. an inverter shut-down, a short circuit in the electric machi-ne and a failure in the regenerative braking system. These three specific faults were further analysed with real

drivers in two test track experiments and a driving simulator study. Both trials had their own particular driving conditions designed for studying the effects of the different failures in detail. Simulator conditions focused on high speed tests, such as in highway driving situations, whereas test track trials targeted urban speed ranges. The results illustrate the driver’s ability to compensate for these failures, with varying types of effort, and regain control of the vehicle. Future research should focus on the possibility of supporting the driver at better coping with failure situations as well as try to shed light on which elements of the driving task (traffic, distractions, speed, etc.) affect the driver’s capability to do so.

For more detail on the active safety investigations by EVERSAFE, please refer to “Deliverable 2.1 – Driver and Vehicle Behaviour to Power Train Failures in Electric Vehicles”¹.

Studying driver response and vehicle behavior in case of failure in electrical powertrain. Photo: David Krems, MADK Photography – Fotografie Köln

Image: Thinkstock

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Passive safety aspects for vehicles with traction batteries were consi-dered in EVERSAFE. The layout of vehicle components is sensitive to the mechanical loading expected in collisions. A review of the distribution of crash types involving high acce-leration or high deformations were studied to establish relevant load cases. Specific queries of databases to identify traction battery incidents were also conducted as well as a battery placement study. An FE model of an electric vehicle together with its critical sub compo-nents was developed. Simulations were performed using load cases arising from standard colisions as well as those load cases which could be identified from real world colisions. The latter were taken in consideration in order to establish critical conditions for the energy storage system (ESS) which might not be fully addressed in current regulations and standards.

Passive Safety Studies and Battery SafetyThe outcomes of the simulation activities served as a basis for experimental tests with ESS and their components as well as whole vehicle crash tests, two of which were performed in EVERSAFE. For the tested conditions, only severe deformations at the cell level compromised battery safety. The battery cells evaluated in the project (currently used in automo-tive high-voltage batteries) have been proven to be more resistant to abuse than initially expected indicating that current standards for electric vehicle components have already reached high safety levels. However, a need for extend testing beyond current standard procedures has been identified. The statement above regarding the safety levels of components in electric vehicles, holds from the point of view of mechanical loading as well as from an electro-chemical perspective since both these

issues were under analysis for the majority of the experiments. Moreover, it is important that rescue crews are able to quickly identify and tackle any threats that might arise in a post-crash situation. The majority of rescue guidelines existing today for electrified vehic-les are based on those existing for their ICE (Internal Combustion Eng-ine) counterparts. Such guidelines were reviewed in light of the project findings, in an effort to pinpoint possible needs for improvement to the latter when the focus shifts to EVs. This leads to the creation of an updated set of guidelines which can be used as a replacement or comple-ment to the ones existing today.

A complete overview of the passive safety investigations can be found in “D3.1 - Recommendations and Guidelines for Battery Crash Safety and Post-Crash Safe Handling¹.

Developed Battery pack for simulations within the passive safety scope. Image: Fraunhofer Institute for High-Speed Dynamics – Ernst-Mach-Institut (EMI)

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New Safety Requirement and Future Research

Eversafe Newsletter 2

The results of the investigations performed for the passive and active safety categories defined in EVERSAFE were used to compile sets of safety recommendations in terms of future research, standards and potential new/updated regula-tions. From a passive safety scope, the need to further study the influence of stiff battery structures on vehicle acceleration pulses, has been identified. Suggestions for updates of UN Regulations – 94/95 have been formulated in order to handle the measurement of toxic/flam-

mable gases in addition to liquid electrolyte in crash tests. Furthermore, recommendations for standards on identification and location of ser-vice disconnects for traction (high voltage) power system are suggested carrying some improvement of post-crash handling. When considering the active safety investigations, the majority of the findings led to the need for further research. It was understood that failures on an electrical powertrain can have potentially hazardous outcomes for the vehicle stability and occupant safety. The project pointed

out a need for future research on the influence of driver workload over the ability to counter the consequences of a failure, as well as the implica-tions of a more complete driving task/ condition (weather, road conditions, traffic, etc.), over the management of fault implications.

For the complete documentation about the project outcomes please consult “Deliverable 4.2 – Recom-mendations for New Safety Require-ments and Research”¹.

¹All public material is available at www.eversafe-project.eu.

Research tools and activities carried out by the EVERSAFE consortium. Image: BASt, Fraunhofer Institute for High-Speed Dynamics – Ernst-Mach-Institut (EMI), KTH, TU Chemnitz, VTI